Were you trying to post a photo? When composing your message, click the "Insert/Edit Image" icon at the top of the text box. It's near the center and it's a square with a pair of mountain peaks in it. You'll get instructions from there. Keep in mind that RAW files are not supported by the average web browser, to please try to stick to commonly-supported formats such as JPG.
We hope this helps, and we look forward to seeing what you share!